1. Scientific Measurement

2. Nature of Measurement Examples:
Measurements are fundamental to the experimental sciences.
Important to make measurements
Important to decide whether a measurement is correct
Measurement - quantitative observation consisting of 2 parts
Part 1 - number
Part 2 - scale (unit)
Examples:
20 grams
6.63 x 1034 atoms

3. Precision & Accuracy
Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several measurements made in the same manner.
Neither accurate nor precise
Precise but not accurate
Precise AND accurate

4. Uncertainty in Measurement
A measurement always has some degree of uncertainty.
A digit that must be estimated is called uncertain.

5. Why Is there Uncertainty?
Measurements are performed with instruments. No instrument can read to an infinite number of decimal places
Which of these balances has the greatest uncertainty in measurement?

6. Reading the Meniscus
Always read volume from the bottom of the meniscus.
The meniscus is the curved surface of a liquid in a narrow cylindrical container.

7. Measuring Volume
Determine the volume contained in a graduated cylinder by reading the bottom of the meniscus at eye level.
Read the volume using all certain digits and one uncertain digit.
Certain digits are determined from the calibration marks on the cylinder.
The uncertain digit (the last digit of the reading) is estimated.

8. Use the graduations to find all certain digits
There are two unlabeled graduations below the meniscus, and each graduation represents 1 mL, so the certain digits of the reading are…
52 mL.

9. Estimate the uncertain digit and take a reading
The meniscus is about eight tenths of the way to the next graduation, so the final digit in the reading is…
0.8 mL
The volume in the graduated cylinder is
52.8 mL.

10. 10 mL Graduate
What is the volume of liquid in the graduate? 6
_ . _ _ mL 6 2

11. 25mL graduated cylinder _ _ . _ _ mL 1 1 5 1
What is the volume of liquid in the graduate?
_ _ . _ _ mL 1 1 5 1

12. The cylinder contains:
Self Test
Examine the meniscus below and determine the volume of liquid contained in the graduated cylinder.
The cylinder contains: 7
_ _ . _ mL 6

13. The Thermometer Read the scale on the thermometer at eye level.
Read the temperature by using all certain digits and one uncertain digit.
Certain digits are determined from the calibration marks on the thermometer.
The uncertain digit (the last digit of the reading) is estimated.

14. Do not allow the tip to touch the walls or the bottom of the flask.
If the thermometer bulb touches the flask, the temperature of the glass will be measured instead of the temperature of the solution. Readings may be incorrect, particularly if the flask is on a hotplate or in an ice bath.

15. Reading the Thermometer
Determine the readings as shown below on Celsius thermometers:
_ _ . _ C 8 7 5
_ _ . _ C 3 5

16. Determining Mass 1. Place object on pan
2. Move riders along beam, starting with the largest, until the pointer is at the zero mark

17. Check to see that the balance scale is at zero

18. 1 1 4
? ? ?
_ _ _ . _ _ _
Read Mass

19. 1 1 4 4 9 7
_ _ _ . _ _ _
Read Mass More Closely

20. The Fundamental SI Units (ie: Système International, SI)
Physical Quantity
Name
Abbreviation
Mass
kilogram kg
Length
meter m
Time
second s
Temperature
Kelvin K
Amount of Substance
(1 mol = 6.02x1023)
mole
mol

21. BASE UNIT SI Prefix Abbr Exp Meaning Equality mega M 106 kilo k 103
1 million x larger
1,000,000 base unit = 1 M_
kilo k
103
1,000 times larger
1,000 base unit = 1 k_
deca da 10
10 times larger
10 base unit = 1 D_
BASE UNIT
(meters, grams, liters, etc.) 1
1 base unit
deci d
10-1
1/10
1 base unit = 10 d_
centi c
10-2
1/100
1 base unit = 100 c_
milli m
10-3
1/1,000
1 base unit = 1,000 m_
micro 
10-6
1/million
1 base unit =
1,000,000 _
nano n
10-9
1/billion
1,000,000,000 n_
pico p
10-12
1/trillion
1,000,000,000,000 p_

22. Y Z E P T G M k h da d c m µ n p f a z y
FACTOR
...or in full ...
or in words
SI PREFIX
SI SYMBOL
1,0E+24 1,0E+21 1,0E+18 1,0E+15 1,0E+12 1,0E+9 1,0E+6 1,0E+3 1,0E+2 1,0E+1 1,0E-1 1,0E-2 1,0E-3 1,0E-6 1,0E-9 1,0E-12 1,0E-15 1,0E-18 1,0E-21 1,0E-24
,1 0,01 0,001 0, , , , , , ,
septillion sextillion quintillion quadrillion trillion billion million thousand hundred ten tenth hundredth thousandth millionth billionth trillionth quadrillionth quintillionth sextillionth septillionth
yotta- zetta- exa- peta- tera- giga- mega- kilo- hecto- deca- deci- centi- milli- micro- nano- pico- femto- atto- zepto- yocto-
Y Z E P T G M k h da d c m µ n p f a z y

23. SI Basic Units & Quantities
Length = meter (m)
Volume =
volume of 1m x 1m x 1m cube = 1 m3
More convenient = liter (L)
1 cm3 = 1 mL
10 drops H2O ≈ 1 mL
Mass = kilogram (kg)
Defined as the mass of 1 L of 4ºC
weight is a force that measures the pull on a given mass by gravity

24. SI Basic Units & Quantities
Temperature =
Celsius (°C) -
Water 0 °C
Water 100 °C
Kelvin (K) - the absolute scale
Don’t use the degree symbol
Water 273 K
Water 373 K
K = °C + 273
°C = K - 273

25. Practice Simple Conversions
5m to cm
2.3 cm to mm
87mm to cm
935 mm to m